Electrophoretic display

ABSTRACT

The present invention is directed to an electrophoretic display comprising: (a) microcups comprising partition walls and top-openings; (b) an organic-based electrophoretic fluid filled in the microcups, wherein said fluid comprises charged pigment particles dispersed in a solvent; and (c) a top-sealing layer formed from a sealing composition to enclose the electrophoretic fluid within the microcups. The sealing composition comprises: (i) a water soluble polymer, (ii) a water-based suspension, a water-based dispersion, a water-based emulsion, or a water-based latex, each comprising a polymer; and (iii) water.

This application is a continuation-in-part of U.S. application Ser. No.11/774,773, filed Jul. 9, 2007; which claims the benefit of U.S.Provisional Application No. 60/831,779, filed Jul. 18, 2006. Theabove-identified applications are incorporated herein by reference intheir entirety.

BACKGROUND OF THE INVENTION

Various structures with peripheral plates or walls containing a liquidcomponent were previously known. For example, a liquid component may befilled between two parallel or near-parallel surfaces and, in such acase, the liquid component is present in a continuous form. The twoplates may be edge sealed first with fill holes for subsequent fillingof the liquid component. Alternatively, the liquid component may bedropped on one of the two plates (before or after application of theedge sealing adhesive), followed by placing a second plate on top of thefirst plate to contain the liquid component between the two plates. Insome cases, spacers may be present in the continuous liquid phase tocontrol the distance between the two plates. However, such a continuousliquid phase structure suffers certain disadvantages. For example, itlacks structure integrity and depth control, especially when the platesare flexible substrates. In addition, this type of structure is notformat flexible for production and, if hard surface plates are involved,batch manufacturing is required which results in low productionefficiency.

It is also possible to divide a liquid component into smallcompartments, for example, by microencapsulation. Individual dropletsare wrapped by a wall material to form discreet compartments and suchcompartments are arranged between two parallel or near-parallelsurfaces. There are numerous examples of microencapsulation of a liquidcomponent for different types of applications. In the display field, forexample, there are encapsulated electrophoretic displays andencapsulated cholesterol liquid crystal displays. In the pharmaceuticalfield, drugs may be encapsulated for controlled release. In the imagingfield, dye and UV curable monomers may be encapsulated forlight/pressure induced imaging development. In this approach, theperformance of an encapsulated product or device often depends on thesize distribution of the microcapsules. It could be challenging tocontrol the size of the microcapsules to be within a desired range. Inaddition, the capsule wall usually does not provide good mechanicalsupport for structural integrity, especially with flexible substrates.Material selection is another issue with the microencapsulationtechnique. In many cases, extra chemical(s) are necessary to stabilizethe dispersed phase; the extra chemical(s), however, could bedetrimental to the final product.

U.S. Pat. No. 6,930,818 and related patents and patent applicationsdescribe a microcup structure for monochrome or multi-colorelectrophoretic displays. An electrophoretic display device is formedwhen the microcups are filled with an electrophoretic fluid comprisingcharged pigment particles dispersed in a dielectric solvent or solventmixture. U.S. Pat. No. 6,795,138 and related patents and patentapplications disclose a liquid crystal display, also utilizing themicrocup structure. The liquid crystal composition filled in themicrocups may further comprise one or more guest dye(s), in particular,dichroic dye(s). US Patent Application Publication No. 2005-0012881Adescribes a display device which can display a 3-dimensional image andsuch a display device is formed when the microcups are filled with anoptically active electrophoretic dispersion. US Patent ApplicationPublication No. 2006-0139724 discloses an electrodeposition orelectrochromic display device which is formed when the microcups arefilled with an electrolyte fluid or an electrochromic fluid. Thecontents of all of the patents and patent applications referred to aboveare incorporated herein by reference in their entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a film structure of the present invention.

FIGS. 2 a and 2 b illustrate microembossing processes.

FIGS. 3 a-3 c illustrate the imagewise exposure processes for thepreparation of microcups.

FIGS. 4 a-4 c show the structures of display devices prepared from thefilm structure of the present invention.

FIGS. 5 a-5 d show how a semi-finished display panel may be converted toa finished display panel.

FIG. 6 illustrates a process involving a film structure containing onesingle liquid composition.

FIGS. 7 a-7 h illustrate a process involving a film structure containingmore than one liquid composition.

FIG. 8 depicts an example of a transdermal delivery film.

FIG. 9 illustrates a display device in which the inside surface of thedisplay cells (e.g., microcups) are coated with a conductive layer.

SUMMARY OF THE INVENTION

The present application describes a film structure which comprises oneor more microcups and the microcups are filled with a liquid compositionand top-sealed with a sealing layer which is hardened in situ.

The first aspect of the present invention is directed to a liquidcrystal display, utilizing the film structure. The liquid crystaldisplay comprises (a) one or more microcups comprising partition wallsand top-openings, (b) a liquid crystal composition filled in themicrocups which liquid crystal composition comprises liquid crystals anda polymer matrix or a three-dimensional polymer network; and (c) asealing layer to enclose the liquid crystal composition within themicrocups which sealing layer is hardened in situ. The liquid crystalcomposition is formed by hardening a precursor composition comprisingliquid crystals and a polymer precursor. The precursor composition maybe hardened before or after hardening of the sealing layer, orsimultaneously when the sealing layer is being hardened.

Alternatively, the liquid crystal composition in the liquid crystaldisplay may comprise liquid crystals, a chiral material and optionally apolymer network.

In another embodiment of the present invention, a display device may beprepared by (1) forming a film structure comprising microcups on asubstrate, (2) forming a first conductive layer on the inside surface ofthe microcups including the side surface and bottom surface of themicrocups and the top surface of the partition walls, (3) filling themicrocups with a display fluid and sealing the filled microcups, and (4)laminating or depositing a second conductive layer onto the filled andsealed microcups, optionally with an adhesive layer. If the secondconductive layer is deposited by, for example, printing, thin filmsputtering or vapor deposition, a second substrate layer may belaminated onto the second conductive layer, optionally with an adhesivelayer. In this embodiment, the first conductive layer is placed betweenthe microcup surface and the display fluid. Optionally, an electrodeprotective layer, a textured layer, an alignment layer, an anchoringlayer, or other performance enhancement layers may be coated onto thefirst conductive layer before the filling and sealing of the displayfluid. Any of the display fluids disclosed in this application may beused in this embodiment of the invention.

The second aspect of the present invention is directed to a transdermaldelivery system, utilizing the film structure. The transdermal deliverysystem comprises (a) one or more microcups comprising partition wallsand top-openings; (b) a liquid composition filled in the microcups whichliquid composition comprises a medicinal or cosmetic agent; and (c) asealing layer to enclose the liquid composition within the microcupswhich sealing layer is hardened in situ. The microcups in thetransdermal delivery system may be filled with liquid compositionscontaining different medicinal or cosmetic agents.

Using the film structure, a liquid composition is filled into individualmicrocups and the filled microcups are top-sealed. The size of themicrocups can be predetermined and controlled. In addition, the microcupwall is in fact a built-in spacer to keep the top and bottom substratesapart at a fixed distance. The mechanical properties and structuralintegrity of the film structure are significantly improved. Furthermore,the use of the film structure eliminates the need of an edge sealadhesive required in the formation of a display panel. More importantly,the microcup-based film structure enables a format flexiblemanufacturing process wherein the process produces a continuous outputof the film structure in a large sheet format which can be cut into anydesired sizes afterwards.

DETAILED DESCRIPTION OF THE INVENTION I. Film Structure

FIG. 1 illustrates the film structure (10), a electrophoretic display,which comprises one or more microcups (11). The microcups comprisepartition walls (16) and top openings (17). The film structure (10) maybe formed on a substrate layer (12) which may optionally comprise anelectrode layer (not shown). There may also be an optional primer layer(15) between the microcups and the substrate layer (12). The microcupsare filled with a liquid composition (13) and top-sealed with apolymeric sealing layer (14).

1. Formation of the Microcups

(a) Microembossing

This processing step is shown in FIGS. 2 a and 2 b. A male mold (20) maybe placed either above (FIG. 2 a) or below (FIG. 2 b) the web (24). Themicrocups may be formed on a flexible substrate layer (21). Thesubstrate layer (21) may optionally comprise an electrode layer (notshown), which is suitable especially for display applications or otherapplications the operation of which involves the application of avoltage or current. The electrode layer, if present, usually is atransparent conductor film on the substrate layer. Alternatively, thesubstrate layer may be rigid and in such a case, the microcup layer maybe fabricated by batch processes.

A layer of an embossable composition (22), such as a thermoplastic orthermoset precursor, is coated on the substrate layer (21). Theembossable composition is embossed by the male mold (20) in the form ofa roller, plate or belt, at a temperature higher than the glasstransition temperature (or Tg) of the embossable composition.

Hard embossing may also be used. Conventional isothermal embossingtechnique comprises the steps of heating both a mold and a substrate toa temperature above the glass transition temperature (Tg) of thesubstrate. In this process, the top surface of the substrate is heatedbefore embossing by passing it through an oven, an IR heater and/or hotrollers. If a non-isothermal embossing process is used, the processinvolves heating only the mold to a temperature higher than the Tg of atop surface to be embossed. Embossing can be done directly on the topsurface of a web (e.g., a thermoplastic web) or on the top surface of athermoplastic polymer layer applied onto a web. In either case, the webhas to be cooled before releasing from the mold to maintain a goodembossing structure.

The embossable composition may be a multifunctional acrylate ormethacrylate, vinylether, epoxide, an oligomer or polymer thereof or thelike. Multifunctional acrylate and its oligomers are the most preferred.A combination of a multifunctional epoxide and a multifunctionalacrylate is also very useful to achieve desirable physico-mechanicalproperties. A crosslinkable oligomer imparting flexibility, such asurethane acrylate or polyester acrylate, may also be added to improvethe flexure resistance of the microcups formed. The embossablecomposition may further contain an oligomer, monomer, additives andoptionally a polymer. The glass transition temperatures for this classof materials usually range from about −70° C. to about 150° C.,preferably from about −20° C. to about 50° C. The microembossing processis typically carried out at a temperature higher than the Tg. A heatedmale mold or a heated housing substrate against which the mold pressesmay be used to control the microembossing temperature and pressure.

As shown in FIGS. 2 a and 2 b, the mold is released during or after theembossable composition is hardened to reveal the microcups (23). Thehardening of the embossable composition may be accomplished by cooling,cross-linking by radiation, heat or moisture. If the curing of theembossable composition is accomplished by UV radiation, UV may radiateonto the substrate layer (21) which must be transparent from the bottomor the top of the web as shown in the two figures. Alternatively, UVlamps may be placed inside the mold. In this case, the mold must betransparent to allow the UV light to radiate through the mold onto theembossable composition.

Optionally, the microcup surface (i.e., the inside surface of themicrocups in direct contact with the liquid composition) may be furthermodified after or during the microembossing process in order for adisplay device to achieve optimal performance. For example, for a LCDdisplay device, an alignment layer or anchoring layer may be fabricatedon the microcup surface. Polyimide, polyvinyl alcohol, polyamide,silicon dioxide, nylon, lecithin or a photoalignment material may becoated onto the microcup surface after microembossing, which may beaccompanied by subsequent rubbing or photo exposure. In anotherscenario, the surface of the microcups may be textured which could beachieved by forming ordered micro-structures (for example, micro-groovestructures with controlled incline angles) on the surface of the malemold. The micro-structures may be initially created on a photoresistlayer during the LIGA (i.e., lithography, electroforming and molding)process for the mold fabrication, or engraved onto the male mold bydiamond turn after the electroforming step. Through embossing, themicro-structures on the male mold will be transferred to the microcupsurface. Such micro-structures may be used to enhance the anchoring orcontrol of the alignment and the pretilt angle of the liquid crystals.As a result, the performance of the liquid crystal display device isenhanced.

Within the microcups, there may be vertical protruding sub reliefstructures (e.g., acting as spacers) arising from the bottom of themicrocups. The sub relief structures may be discrete structures such ascolumns, cylinders, wedges, crosses or continuous structures such aswalls and grids. The top surface of the continuous sub structures may beof any shape and is preferred to be no larger than the bottom of thestructures. The cross-section of the sub relief structures can be of anyshapes, including round, square, rectangle, oval and others. Such subrelief structures may be prepared by microembossing or photolithography.Details of this feature are described in U.S. Pat. No. 6,947,202, thecontent of which is incorporated herein by reference in its entirety.The sub relief structures may be of the same height or lower than themicrocup walls.

One of the examples for the preparation of the male mold is given inU.S. Pat. No. 6,930,818.

(b) Imagewise Exposure

Alternatively, the microcups may be prepared by imagewise exposure (FIG.3 a) of a radiation curable material (31) coated on a substrate layer(33) which may be flexible or rigid, to UV or other forms of radiationthrough a photomask (30). The substrate layer (33) may also comprise anelectrode layer (32), depending on the application of the final deviceformed. In other words, electrode layer (32) in the figure may or maynot be present. The electrode layer (32) may be present if the operationof the intended final product involves the application of a voltage orcurrent, such as a display device. The electrode layer, if present, is aconductor film on the substrate layer.

For a roll-to-roll process, the photomask may be synchronized with theweb and move at the same speed as the latter. In the photomask (30) inFIG. 3 a, the dark squares (34) represent the opaque area and the space(35) between the dark squares represents the opening area. The UVradiates through the opening area (35) onto the radiation curablematerial (31). The exposed areas become hardened and the unexposed areas(protected by the opaque area in the mask) are then removed by anappropriate solvent or developer to form the microcups (36). The solventor developer is selected from those commonly used for dissolving orreducing viscosity of radiation curable materials, such asmethylethylketone, toluene, acetone, isopropanol or the like.

FIGS. 3 b and 3 c illustrate two other options for the preparation ofmicrocups by imagewise exposure. The features in these two figures areessentially the same as shown in FIG. 3 a and the corresponding partsare also numbered the same.

In FIG. 3 b, the substrate (33) is opaque and pre-patterned. Theelectrode layer (32) is optionally present. In this case, the substratelayer (and the electrode layer if present) serves as a photomask. Themicrocups (36) can then be formed by removing the unexposed areas afterUV radiation.

In FIG. 3 c, the substrate layer (33) is also opaque and pre-patterned.The radiation curable material is exposed from the bottom through aline-pattern on the substrate layer (33) (and the electrode layer 32 ifpresent) which also serves as the first photomask. A second exposure isperformed from the other side through the second photomask (30) having aline pattern perpendicular to the first set of lines. The unexposed areais then removed by a solvent or developer to reveal the microcups (36).

(c) Pre-Punched Holes

The microcups may also be prepared by laminating a spacer film with anarray of prepunched holes onto a substrate layer. Suitable spacer filmmaterials for having prepunched holes may include thermoset orthermoplastic resins such as polyethylene terephthalate (PET),polyethylene naphthalate (PEN), polycarbonate, polymethyl methacrylate(PMMA), polysulfone, polystyrene, polyurethane, polysiloxanes, epoxyresins, polyolefins, polycycloolefins, polyamides, polyimides, curedvinyl esters, cured unsaturated polyesters, cured multifunctional vinylethers, cured multifunctional acrylates, cured multifunctional allylsand copolymers thereof. The spacer film may be clear, opaque or colored.The lamination of the film may be accomplished by using an adhesive,such as a pressure sensitive adhesive, a hot melt adhesive, a heat,moisture or radiation curable adhesive. Alternatively, the pre-punchedspacer film may be laminated onto the substrate by heat or by using asuitable solvent for the spacer film, followed by drying. Examples ofsuitable solvents include THF, acetone, methylethylketone,cyclohexanone, ethyl acetate and derivatives thereof and these solventsare particularly useful for PMMA and polycarbonates. The substrate layermay optionally comprise an electrode layer.

There may be a primer layer (15) between the microcups and the substratelayer, which primer layer may be formed from a material such aspolyacrylate, polyurethane, polyurea, polystyrene, polybutadiene,polyester, polyether, cellulose resins, phenolic resins, melamineformaldehyde resins or a combination thereof. The material for theprimer layer may be the same as the material used for the formation ofthe microcups.

In general, the microcups can be of any shape, and their sizes andshapes may vary. The microcups may be of substantially uniform size andshape in one system. However, it is possible to have microcups of mixedshapes and sizes.

The openings of the microcups may be round, square, rectangular,hexagonal or any other shape. The size of the partition area between theopenings may also vary.

The dimension of each individual microcup without sub relief structuresmay be in the range of about 1×10¹ to about 1×10⁶ μm², preferably fromabout 1×10² to about 1×10⁶ μm² and more preferably from about 1×10³ toabout 1×10⁵

With the presence of the sub relief structures, the microcup may be inthe range of about 1×10² to about 1×10⁸ μm², more preferably from about1×10³to about 10⁷ μm².

The depth of the microcups may be in the range of about 5 to about 200microns, preferably from about 10 to about 100 microns. The opening tothe total area ratio is in the range of from about 0.05 to about 0.95,preferably from about 0.4 to about 0.9.

2. Liquid Composition

The term “liquid composition”, in the context of the present invention,refers to the composition which is filled in the microcups and isbroadly defined as a substance that has the tendency to flow. It may bea solution, suspension/dispersion, emulsion, gel or the like. The liquidcomposition can be water based, organic based or silicone orfluorocarbon based.

The liquid composition filled into the microcups may be one singleliquid composition or a mixture of two or more liquid compositions.

In addition, not all of the microcups have to be filled with the sameliquid composition. For example, for display applications, the microcupsmay be filled with display fluids of different colors to generatedifferent colors in different areas. As a result, a display device mayhave a certain number of microcups filled with a liquid composition of afirst color, a certain number of microcups filled with a liquidcomposition of a second color and so on.

The filling of the liquid composition into the microcups may beaccomplished by a conventional printing technique, such as inkjet,gravure, screen printing, spray printing or strip coating.

For pharmaceutical applications, different liquid compositions which arephysically incompatible may be filled in different microcups. The ratioof the microcups filled with different liquid compositions may bepre-determined. For example, in a pharmaceutical device (i.e., atransdermal delivery system), some of the microcups may be filled withone liquid composition comprising a first active ingredient while othermicrocups may be filled with another liquid composition comprising asecond active ingredient. The ratio of the two groups of microcups maybe determined by the target doses of the two active ingredients. Such afeature is possible with the present invention because each microcup isa discreet and sealed unit, intermixing of different liquid compositonsis not likely to occur.

It is noted that after being filled into the microcups, the liquidcomposition may change its physical state (i.e., turned into a solid,semi-solid or elastic state). A liquid crystal composition comprising amixture of liquid crystals and a polymer precursor may also bepolymerized and phase separated after being filled into the microcups

There are a variety of liquid compositions suitable for the presentinvention.

A reverse emulsion electrophoretic display may be formed from thepresent film structure. A reverse emulsion comprises a mixture of apolar solvent (e.g., DMSO, DMF, dimethylacetamide, dimethyl sulfone,sulfonlane, hexamethylphosphoric triamide, higher amides, methanol,ethanol, glycols, nitromethane, acetonitrile, water, methoxyethanol,methyl cellosolve or monoethyl ethers) and a non-polar solvent (e.g.,C₁₋₃₀ alkanes,

C₂₋₃₀ alkenes, C₃₋₃₀ alkynes, C₃₋₃₀ aldehydes, C₃₋₃₀ ketones, C₂₋₃₀ethers, C₃₋₃₀ esters, C₃₋₃₀ thioesters, C₃₋₃₀ thioethers, terpenes,C₂₋₃₀ organosilanes or C₂₋₃₀ organosiloxanes, each of which may becyclic or acylic and may be optionally substituted with halides or othernon-polar substituents) and a hydrophilic dye. Suitable hydrophilic dyesmay include, but are not limited to, cationic or anionic monoazo dyes,cationic or anionic diazo dyes, triphenylmethane dyes, pyrazolone dyes,acridines, charged porphyrines, oxazines, diformzans, colored metal andtransition metal complexes, metal salts, acid anthraquinone dyes,amphoteric anthraquinone dyes, cationic diphenylmethane dyes, chargedpolymethine dyes, thiazines, charged phthalocyanines, formazans, andtetrazolium dyes. The solvent mixture may be stabilized with asurfactant and the dye may be present only in the non-continuous polarphase droplets. The droplets can be charged or can be otherwiseresponsive to an electric field. This property of the droplets is usedto arrange the droplets within a pixel. The primary behavior of interestis that the droplets may spread out over the area of the pixel whichresults in a colored pixel or the droplets may be compacted whichresults in a transparent pixel.

Polymer dispersed liquid crystals (PDLC), reverse-mode PDLC, polymernetwork liquid crystals (PNLC), polymer encapsulated liquid crystals(PELC), ferroelectric liquid crystals, cholesteric liquid crystals orpolymer stabilized cholesteric texture (PSCT) may also be used as theliquid composition.

A polymer dispersed liquid crystal (PDLC) display device usually has ahigher polymer concentration (in the form of a polymer matrix) at about20% to about 80% by weight and the liquid crystals dispersed randomly inthe polymer matrix are in the form of micron-sized droplets. Such a PDLCfilm can be switched from a translucent state to a transparent statewhen the applied voltage exceeds a threshold.

For a composition of polymer network liquid crystals (PNLC) or polymerstabilized cholesteric texture, the polymer concentration is relativelylow (e.g., below 30%) and the polymer in the composition forms athree-dimensional network to stabilize the liquid crystals or thecholesteric texture. These compositions are generally in a continuousstate. The composition filled into the microcups is a homogeneousmixture of liquid crystals and a polymer precursor. As athree-dimensional polymer network is formed, by radiation or thermally,the liquid crystals and the polymer form two separate phases.

In the preparation of a polymer dispersed liquid crystal display deviceor polymer network liquid crystal display device utilizing the filmstructure, a precursor composition comprising liquid crystals and apolymer precursor in the state of an isotropic liquid is first filledinto the microcups, followed by sealing the liquid composition withinthe microcups. After the filled microcups are sealed, the filled andsealed microcups are irradiated by a UV light to cause phase separationof a polymer formed from the polymer precursor, from the liquidcrystals. Alternatively, the precursor composition may be first filledinto the microcups, followed by radiation curing to form the PDLC orPNLC morphology and finally the sealing step. In the latter case,nitrogen blanket or Argon protection is preferably used during radiationcuring of the liquid crystal composition to minimize the effect ofoxygen inhibition.

The polymerization of the polymer precursor in either case may beachieved by radiation, thermally or other means, such as electron beams.

In the final product prepared from any of these methods, a liquidcrystal composition comprising a polymer matrix or three-dimensionalpolymer network and liquid crystal droplets forms discrete units whichare separated by microcup partition walls and enclosed in the individualmicrocups.

In the PDLC or PNLC liquid crystal display, the refractive indices ofthe microcups and the sealing layer preferably are matched to therefractive index of the liquid crystals.

Suitable polymer precursors in the precursor composition may include,but are not limited to, acrylates, methacrylates, thiols, alkenes, allylethers. Optionally, a photoinitiator of about 0.01 to about 5% may bepresent to trigger the polymerization. A photoinitiator is selected fromthe group consisting of benzoinether initiators, benzophenone-typeinitiators and thiozanthone-type initiators.

In the precursor composition, the weight ratio of the liquid crystals tothe polymer precursor may range from about 1% to about 80%, preferablyfrom about 2% to about 60%.

A composition of cholesteric liquid crystals comprising liquid crystalshaving positive dielectric anisotropy and a chiral material in an amounteffective to form focal conic and twisted planar textures may also beused as the liquid composition. The chiral material has a pitch lengtheffective to reflect light in the visible spectrum wherein the focalconic and twisted planar textures are stable in the absence of anelectric field and the liquid crystals are capable of changing thetextures upon application of an electric field. Suitable chiralmaterials for this composition may include, but are not limited to,CB15, CE2 and TM74A (manufactured by Merck). A polymer, such as UVcurable thermoplastic and thermosetting polymers, may be further addedto enhance the stability of the image, as in a polymer stabilizedcholesteric texture. The chiral material needs to be selected, dependingon the liquid crystals used, for optimal performance.

The composition of cholesteric liquid crystals may further comprise apolymer network. In addition, the inside surface of the microcups may betextured. It is also possible to have an alignment or anchoring layerfabricated on the inside surface of the microcups. The sealing layer mayalso serve as an alignment or anchoring layer.

The concentration of the chiral material may range from about 0.5% toabout 30% if there is a polymer present in the composition or range fromabout 20% to about 70% if there is no polymer present in thecomposition.

The liquid composition may also be a display fluid as described in U.S.Pat. Nos. 4,126,854, 5,754,332, 6,497,942 and 6,588,131, the contents ofall of which are incorporated herein by reference in their entirety.Briefly, the liquid composition of a so-called twisting ball displaydevice may comprise millions of small beads randomly dispersed in adielectric fluid. The beads, each contained in an oil-filled cavity, arefree to rotate within those cavities. The beads are “bichromal” withhemispheres of two contrasting colors (e.g., black and white, red andwhite), and charged so they exhibit an electrical dipole. When a voltageis applied, the beads rotate to present one colored side to the viewer.

The liquid composition may be a nematic colloid. The nematic colloid maycomprise nematic liquid crystals, nanoparticles of silica and/or clay.The regular nematic liquid crystals (positive dielectric anisotropy)usually switch in one direction under an applied voltage, from aninitial scattered state to a homeotropic transparent state, which isstabilized by an internal volume nanoparticle network and retained afterswitching off the applied voltage.

The liquid composition may also be an electrophoretically controllednematic liquid crystal composition. In this case, polarity controlledelectromigration of the nanoparticles results in the stabilization ofmolecular alignment and provides bistable or multistable switching in aconventionally designed liquid crystal structure.

The liquid composition may also be a guest-host liquid crystalcomposition. Such a composition comprises nematic liquid crystals anddichroic dye(s). The dichroic dye absorbs a light component whoseoscillation face is parallel to the major axis of the dichroic dye. Inaddition, a light component whose oscillation face perpendicular to themajor axis of the dichroic dye is transmitted through the guest-hostliquid-crystals. The nematic liquid crystals (host) and the dichroic dye(guest) are aligned homogeneously under no applied-voltage. Under anapplied voltage, the nematic liquid-crystal molecules, as well as thedichroic dye, are aligned perpendicular to the direction of an electricfield. Light can be modulated to be absorbed or transmitted through theguest-host liquid crystals, thus absorption contrast can be created.

The film structure may also be used for pharmaceutical applications, inparticular as a transdermal delivery device (e.g., plaster or patch).Such a delivery device may be used for local or systemic drug delivery.The liquid composition, in this case, comprises an active ingredientwhich may be a medicinal or cosmetic agent. The medicinal agent mayinclude substances intended for use in the diagnosis, cure, mitigation,treatment or prevention of diseases, or to affect the structure orfunction of the body. The medicinal agent may be a single chemicalentity or a pharmaceutically acceptable salt thereof which will bepresent in an amount such that the device delivers a therapeuticallyeffective amount for the indication being treated. The amount thatconstitutes a therapeutically effective amount will vary according tothe type of the medicinal agent used, the condition to be treated, anymedicinal agents being coadministered, the amount of time thecomposition is allowed to remain in contact with the skin of thepatient, and other factors known to those of skill in the art.

The active ingredient present in the liquid composition will generallybe about 0.01 to about 40% by weight, preferably about 1.0 to about 20%by weight, based on the total weight of the composition.

Any drug that is suitable for transdermal delivery can be used in thefilm structure of the present invention. Examples of useful drugsinclude, but are not limited to, anti-inflammatory drugs,antibacterials, antiprotozoals, antifungals, coronary vasodilators,calcium channel blockers, bronchodilators, enzyme inhibitors,antihypertensives, anti-ulceratives, steroidal hormones, antivirals,immunomodulators, local anesthetics, antitussives, antihistamines,narcotic analgesics, peptide hormones, sex hormones, enzymes,antinauseants, anticonvulsants, immunosuppressives, psychotherapeutics,sedatives, anticoagulants, analgesics, antiarrhythmics, antiemetics,contraceptives, anticancer agents, neurologic agents, hemostatics,anti-obesity agents, smoking cessation regimens or the like.

The liquid composition for pharmaceutical applications may also compriseexcipients, such as a solvent, cosolvent, solubilizer, solvent modifier,permeation enhancer, preservative, buffering agent or the like. Thesolvent is the principal component of the liquid composition andpreferably is one in which the active ingredient is soluble or at leastsubstantially soluble or can be made soluble or become soluble, byaddition of a co-solvent or solvent modifier. Suitable solvents may beselected from any of the solvents normally used for medicaments,cosmetics, nutrients or other active agents to be deliveredtransdermally. Preferred solvents include lower alcohols of from 2 to 6carbon atoms, preferably from 2 to 4 carbon atoms and may bemonoalcohols, such as, ethanol, isopropanol or sec-butanol, or polyols,such as, ethylene glycol, propylene glycol, butylene glycol or glycerol.A mixture of solvents may also be used. Other solvents, such as ketone(e.g., acetone or methylethyl ketone), ethers (e.g., ethylether) mayalso be used, in an amount which will be safe and non-toxic. While thesolvent system is generally non-aqueous, water may be used for watersoluble active ingredients and for those active ingredients which arestable in the presence of and not denigrated by the presence of water.When water is present in the solvent, in some cases, it will usuallyconstitute less than about 50 percent, preferably less than about 10percent, more preferably less than about 2 percent, by weight of thetotal solvent although more or less may be used, depending on the activeingredient and as long as the objective of the invention can be met.

Generally, the total amount of solvent(s) will be selected to assuredissolution of the active ingredient and excipients and provide suitableproduct viscosity. The amount of solvent(s) falling within the range offrom about 5 to about 90 percent, preferably from about 25 to about 75percent, based on the total composition, may be used.

The liquid composition preferably is in the form of a solution. Howeverit is also possible to be in form of a suspension/dispersion, emulsion,gel or the like.

3. Sealing of the Filled Microcups

The sealing of the filled microcups may be accomplished in a number ofways. Because the top-openings of the filled microcups are sealed, thesealing may also be referred to as “top-sealing”.

One approach is to disperse a sealing composition in the liquidcomposition. The sealing composition is immiscible with the liquidcomposition and preferably has a specific gravity lower than that of theliquid composition. The two compositions, the sealing compositing andthe liquid composition, are thoroughly mixed and immediately coated ontothe microcups with a precision coating mechanism such as Myrad bar,gravure, doctor blade, slot coating or slit coating. Excess fluid isscraped away by a wiper blade or a similar device. A small amount of aweak solvent or solvent mixture such as isopropanol, methanol or anaqueous solution thereof may be used to clean the residual fluid on thetop surface of the partition walls of the microcups. The sealingcomposition subsequently separates from the liquid composition andfloats on top of the liquid composition.

Alternatively, after the mixture of the liquid composition and thesealing composition is filled into the microcups, a substrate may belaminated on top to control the metering of the mixture of compositionsand to facilitate the phase separation of the sealing composition fromthe liquid composition to form a uniform sealing layer. The substrateused can be a functional substrate in the final structure or can be asacrifice substrate, for example, a release substrate, which can beremoved afterwards.

A sealing layer is then formed by hardening the sealing composition insitu (i.e., when in contact with the liquid composition). The hardeningof the sealing composition may be accomplished by UV or other forms ofradiation such as visible light, IR or electron beam. Alternatively,heat or moisture may also be employed to harden the sealing compositionif a heat or moisture curable sealing composition is used.

Alternatively, the liquid composition may be filled into the microcupsfirst and a sealing composition is subsequently overcoated onto thefilled microcups. The overcoating may be accomplished by a conventionalcoating and printing process, such as blanket coating, inkjet printingor other printing processes. A sealing layer, in this approach, isformed in situ, by hardening the sealing composition by solventevaporation, radiation, heat, moisture, or an interfacial reaction.Interfacial polymerization followed by UV curing is very beneficial tothe sealing process. Intermixing between the liquid composition and thesealing overcoat is significantly suppressed by the formation of a thinbarrier layer at the interface by interfacial polymerization and thesealing is then completed by a post curing step, preferably by UVradiation. To further reduce the degree of intermixing, the specificgravity of the sealing composition preferably is lower than that of theliquid composition. Volatile organic solvents may be used to adjust theviscosity and thickness of the sealing overcoat. Rheology of the sealingcomposition may be adjusted for optimal sealability and coatability.When a volatile solvent is used in the overcoat, it is preferred that itis immiscible with the solvent in the liquid composition.

The components in the sealing composition are very much dependent on thechemical and physical nature of the liquid composition. Preferably, thesealing composition and its solvent have a solubility of less than about10%, preferably less than about 5% and more preferably less than about3%, in the liquid composition or vise versa. However, even if thesolubility is higher than 10%, there are approaches to adjust therheology, for example, viscosity and elasticity, surface tension orinterfacial tension, to avoid intermixing.

In general, the sealing material in the sealing composition may be athermoplastic, thermoset or precursor thereof. Examples of suchmaterials may include, but are not limited to, polyvalent acrylate ormethacrylate, cyanoacrylate, polyvalent vinyl including vinylbenzene,vinylsilane, vinylether, polyvalent epoxide, polyvalent isocyanate,polyvalent allyl, oligomers or polymers containing crosslinkablefunctional groups and the like.

Surfactants may also be added to the sealing composition to improve theadhesion and wetting at the interface between the liquid composition andthe sealing layer. Useful surfactants include both ionic and non-ionicsurfactants, These surfactants may include, but are not limited to, FCsurfactants (from 3M Company), Zonyl fluorosurfactants (from DuPont) andBYK surfactants (from BYK Chemie USA, Inc.), polysiloxane basedsurfactants (e.g., Silwet and Silquest surfactants from OSI Specialties,Inc.), block copolymers of ethylene and propylene oxide, alkylarylpolyethers (e.g., ethoxylation products of lauryl, oleyl, stearylalcohols and ethoxylated nonylbenzene), alkali metal or ammonium saltsof fatty acids; alkyl, aryl or alkyl aryl sulfonates, sulfates,phosphates and mixtures thereof.

Other additives may also be added to the sealing composition to assistin the film formation, to improve sealing stability or to provide otherfunctions necessary for the processing of the final product. Examples ofsuitable additives may include polymeric binder or thickener,photoinitiator, catalyst, filler, colorant, surfactant, plasticizer,antioxidant or organic solvents. The additive may also be a rheologymodifier such as the associative thickener ACRYSOL (from Rohm and HaasCo.), CAB-O-SIL fumed silica (from Cabot Corp.) or photostabilizers suchas ultraviolet light stabilizers commercially available under the tradedesignation TINUVIN from Ciba. Sealing precursors or additives may existas an emulsion or dispersion in the sealing composition.

Other suitable sealing compositions are disclosed in U.S. Pat. No.7,005,468, U.S. patent application Ser. No. 10/665,898 (Publication No.2004-0120024A), Ser. No. 10/651,540 (Publication No. 2004-0112525A) andSer. No. 10/762,196 (Publication No. 2004-0219306A), the contents of allof which are incorporated herein by reference in their entirety.

As the liquid composition can be water based, organic based, silicone orfluorocarbon based. The components in the sealing composition may beselected accordingly.

For the water based liquid composition, the sealing material in thesealing composition may be a hydrophobic organic polymer, such aspolyacylate, polyvinyl ether, polyvinyl acetal, polycarbonate,polystyrene, polyurethane, polyurea, polyester, polyethylene,polypropylene, poly(isoprene), polybutadiene, vegetable, mineral wax,polycarprolactone, polyorthoester, polyanhydride, epoxy resin, alkydresin, polyvinyl chloride, a cellulose derivative or a copolymerthereof. It is also possible to use a silicone polymer or a fluorinatedpolymer, such as polymers with PDMS (polydimethylsilane) sub-units,polymers with perflruocarbon sub-units, polymers with perfluoroethersub-units or copolymers thereof. Monomers or oligomers of similarchemical nature may be present in the sealing composition for furthercuring of the sealing composition. The solvent used in such type ofsealing composition may be an organic solvent, such as alkanes, ketones,ethers, alcohols or a halogenated solvent, such as FC-43 (primarily C₁₂perfluorinated compounds from 3M), a halocarbon oil (from HalocarbonProducts Corporation), a Galden fluid (low molecular weightperfluoropolyethers from Solvay), a low molecular weight Krytox fluid(perfluoroalkylethers from DuPont) or a PDMS containing solvent,depending on the solubility of the sealing material used in thecomposition.

For the organic based liquid composition, the sealing material may be awater soluble polymer with water as the sealing solvent. Examples ofsuitable water soluble polymers or water soluble polymer precursors mayinclude, but are not limited to, polyvinyl alcohol; polyethylene glycol,its copolymers with polypropylene glycol, and its derivatives, such asPEG-PPG-PEG, PPG-PEG, PPG-PEG-PPG; poly(vinylpyrolidone) and itscopolymers such as poly(vinylpyrrolidone)/vinyl acetate (PVP/VA);polysaccharides such as cellulose and its derivatives,poly(glucosamine), dextran, guar gum, and starch; gelatin;melamine-formaldehyde; poly(acrylic acid), its salt forms, and itscopolymers; poly(methacrylic acid), its salt forms, and its copolymers;poly(maleic acid), its salt forms, and its copolymers;poly(2-dimethylaminoethyl methacrylate); poly(2-ethyl-2-oxazoline);poly(2-vinylpyridine); poly(allylamine); polyacrylamide;polyethylenimine; polymethacrylamide; poly(sodium styrene sulfonate);cationic polymer functionalized with quaternary ammonium groups, such aspoly(2-methacryloxyethyltrimethylammonium bromide), poly(allylaminehydrochloride). The sealing material may also include a waterdispersible polymer with water as a formulating solvent. Examples ofsuitable polymer water dispersions may include polyurethane waterdispersion and latex water dispersion. Suitable latexes in the waterdispersion include polyacrylate, polyvinyl acetate and its copolymerssuch as ethylene vinyl acetate, and polystyrene copolymers such aspolystyrene butadiene and polystyrene/acrylate.

In one embodiment, the sealing composition comprises (i) a water solublepolymer as described above, (ii) a water-based suspension, a water-baseddispersion, a water-based emulsion, or a water-based latex, eachcomprising an epoxy resin or a polymer selected from the groupconsisting of polyurethane, polyacrylate, polyvinyl acetate, polyvinylchloride, polystyrene, and the copolymer thereof; and (iii) water;wherein the top-sealing layer is on top of, and in contact with, theelectrophoretic fluid. The sealing composition may further comprise afourth component, i.e., a water soluble or water dispersable UV curablemonomer, oligomer, or polymer such as ethoxylated or propoxylated mono,bi, tri, or multifunctional acrylate; ethoxylated or propoxylated mono,bi, tri, or multifunctional methacrylate; or polymers comprisingsegments that facilitate the water comparability such as polyethyleneglycol or polar groups, e.g., hydroxyl, aimine, acid, etc.Alternatively, the sealing composition may comprise a different fourthcomponent, i.e., a water soluble or water dispersable thermalcrosslinker, coupling agent, or adhesion promoter; such aspolyisocyanate, blocked or encapsulated isocyanate, multifunctionalpolycarbodiimide, multifunctional aziridine, silane coupling agent,epoxy silane, boron/titanium/zirconium based crosslinker, Melamineformaldehydes

It is also possible to use, as a sealing material, a silicone polymer ora fluorinated polymer. Such polymers may be selected from polymers thatconsist of PDMS sub-units or polymers with perflurocarbon sub-units,polymers with perfluoroether sub-units or copolymers thereof. Monomersor oligomers of similar chemical nature may be present in the sealingcomposition for further curing of the composition. Suitable solvents mayinclude solvents such as FC-43, halocarbon oil, a Galden fluid, a lowmolecular weight Krytox fluid or a PDMS containing solvent.

It is also possible to find incompatible organic polymers for certainorganic based liquid composition, as the sealing material. If theorganic solvent based liquid composition is hydrophilic, it may containa significant amount of polymer groups, such as polyethylene oxide,alcohol or nitrile. In this case, the sealing material may be ahydrophobic polymer, such as polyisoprene, polyethylene, polypropylene,polybutadiene, copolymers thereof or the like and the solvent in thesealing composition may be a hydrophobic solvent, such as alkanes.

For a silicon and fluorocarbon based liquid composition, the sealingmaterial may be a water soluble polymer with water as the sealingsolvent in the sealing composition. Examples of suitable water solublepolymers may include, but are not limited to, cellulose polymers,latexes, pseudolatexes, gelatin, polyvinyl alcohol, polyethylene glycol,PEG-PPG-PEG, PPG-PEG, PPG-PEG-PPG, polyvinyl pyrolidone, PVP/VApolysaccharides, starch, melamine-formaldehyde, phospholipids and thelike. The sealing material may also be a hydrophobic organic polymer,such as poly(acylate), polycarbonate, polystyrene, polyurethane,polyethylene, polypropylene, poly(isoprene), polybutadiene, vegetable,mineral wax, polycarprolactone, polyorthoester, polyanhydride, epoxy orcopolymer thereof. Monomers or oligomers of similar chemical nature maybe present in the sealing composition for further curing of the sealingcomposition. The solvent used in the sealing composition may also be anorganic solvent, such as alkanes, ketones, ethers, alcohols or the like.

The sealing layer is one of the critical features of the film structureof the present invention. The sealing composition can be formulated toachieve certain desired chemical or physical properties of the finalproduct. For example, for display applications, the sealing layer, whenproperly formulated, can cut down the voltage drop in order to increasethe effective voltage applied to the display panel.

The sealing layer may also be modified beyond meeting the requirementsof coatability and sealability on the filled microcups. For example, thesealing layer may contain a photo-alignment composition, which uponradiation will create an alignment surface in contact with thecomposition filled in the microcups.

For transdermal delivery applications, the active ingredient permeatesthrough the sealing layer at a desired rate. Diffusion of the activeingredient through the sealing layer is dependent on properties of theactive ingredient, the solvent in which the active ingredient ispresent, the chemical nature of the sealing layer/adhesive layer or anyother layers in between the active ingredient and the skin. The rate ofdiffusion, in general, tends to decrease with increased molecularvolume. The rate of skin penetration, on the other hand, is a functionof the diffusion coefficient, the barrier partitioning tendency, bindingaffinity and the rate of metabolism of the active ingredient by theskin. The sealing layer, in this aspect of the invention, is preferablya continuous or microporous film. A continuous film may be preparedfrom, for example, ethylene:vinyl acetate copolymers which may containan appropriate amount of vinyl acetate, for example, about 0.5 to about40% by weight.

II. Display Device

The film structure (10) of FIG. 1 may be used in a display device.Examples of the liquid composition suitable for display devices arediscussed in Section I.2. FIGS. 4 a-4 c depict various possibleconfigurations of a display device.

In FIG. 4 a, the film structure (40) is sandwiched between two electrodelayers (41 a and 41 b). For illustration purpose, the side marked 40 ais the sealing layer side. There may be a primer layer (42) between thefilm structure (40) and one of the electrode layers (41 a). The primerlayer may be formed from a material such as polyacrylate, polyurethane,polyurea, polysturene, polybutadiene, polyester, polyether, celluloseresins, phenolic resins, melamine formaldehyde resins or a combinationthereof. The material for the primer layer may be the same as thematerial used for the formation of the microcups. The microcups (44) arefilled with a display fluid (i.e., a liquid composition 45) and sealedwith a sealing layer (46). There may also be an adhesive layer (43)between the sealing side of the film structure and one of the electrodelayer 41 b. The display device as depicted may be viewed from thesealing side (if the sealing layer, the adhesive layer if present andthe electrode layer 41 b are transparent) or from the non-sealing side(if the primer layer if present and the electrode layer 41 a aretransparent).

For an in-plane switching mode display device such as the one disclosedin U.S. Pat. No. 6,885,495, the content of which is incorporated hereinby reference in its entirety, the film structure is sandwiched betweenone substrate layer and one electrode layer.

For a display device, one side of the film structure may be a commonelectrode layer and the other side of the film structure may be appliedby a writing pen or a scanning device with a voltage on its bare surfaceto achieve image updating.

FIGS. 4 b and 4 c depict display panels which are referred to as asemi-finished display panel.

In FIG. 4 b, the semi-finished display panel comprises the filmstructure (40) sandwiched between a temporary substrate (47 a) and anelectrode layer or a permanent substrate layer (47 b). The positions ofthe temporary substrate (47 a) and the electrode or permanent substratelayer (47 b) may be switched.

In FIG. 4 c, the film structure (40) is sandwiched between two temporarysubstrate layers (48 a and 48 b).

The display panel or semi-finished display panel may be coated with aprotective layer. The protective layer may be formed from silicone, afluorocarbon compound, polyethylene or polypropylene, and is readilypeeled off.

The primer (42) and adhesive (43) layers may be also optionally presentin any of the semi-finished display panels as exemplified.

The semi-finished display panels may be formed by any of the methodsdisclosed in this application and U.S. patent application Ser. No.10/351,460 (Publication No. 2003-0179436A), the content of which isincorporated herein by reference in its entirety.

The temporary substrate such as a release liner may be formed from amaterial selected from the group consisting of polyethyleneterephthalate (PET), polycarbonate, polyethylene (PE), polypropylene(PP), paper and a laminated or cladding film thereof. A silicone releasecoating may also be applied onto the temporary substrate to improve therelease properties.

The temporary substrate layer may comprise a conductive layer coated oneither side of the temporary substrate layer or the temporary substratelayer may be conductive itself.

The semi-finished display panel may be supplied to customers in the formof a roll and the customers may cut the roll of the semi-finished panelinto desired formats and sizes to meet their specific needs.

The conversion of a semi-finished panel to a finished display panel isexemplified in FIG. 5.

FIG. 5 a depicts a roll of semi-finished display panel. FIG. 5 b depictsa cross-sectional view of a semi-finished display panel comprising afilm structure (50) sandwiched between a temporary substrate (51) and afirst electrode layer or a permanent substrate layer (52). The sidemarked 50 a is the sealing layer side. The temporary substrate (51) islaminated over the film structure, optionally with an adhesive layer (53a) between the film (50) and the temporary substrate (51). The layer 53is a sealing layer. FIG. 5 c depicts that the temporary substrate (51)is peeled off. In FIG. 5 d, a second electrode layer (54) is laminatedonto the film structure. Alternatively, the electrode layer may bedisposed onto the film structure by a method such as coating, printing,vapor deposition, sputtering or a combination thereof.

In the finished display panel shown in FIG. 5 d, either the sealing side50 a or the non-sealing side may be the viewing side.

When the semi-finished panel comprises a film structure is sandwichedbetween two temporary substrate layers, the semi-finished display panelmay be converted to a finished display panel by removing the twotemporary substrate layers, followed by laminating two permanentsubstrate layers, at least one of which comprises an electrode layer,over the film structure. Alternatively, the permanent substrate layersmay be disposed onto the film structure by a method such as coating,printing, vapor deposition, sputtering or a combination thereof.

For display applications, any layer in the path of the electrical fieldmay be further optimized according to the driving method to maximize theeffective driving voltage on the display medium. For example, for DCdriven displays, layers in the path of the electrical field preferablyhave relative low electrical resistance as compared to that of theactive display medium. Low electrical resistance may be achieved bycontrolling the Tg, polarity and the crosslinking density of the polymermatrix of the layer(s), or by adding conductive fillers or fillers oflow resistance to the layer(s). For AC driven displays, these layersprefer to have high dielectric constant. High dielectric constant may beachieved by addition of fillers of high dielectric constant, forexample, Perovskite, barium titanate (BaTiO) or lead titanate (PbTiO3).For current driven displays, these layers prefer to be conductive.Conductivity may be achieved by using conductive polymers or addition ofconductive fillers.

FIG. 9 illustrates a display device prepared by an alternative process.In this process, a film structure comprising microcups (90) is formeddirectly on a first substrate (91). Useful non-conducting substrates mayinclude, but are not limited to, glass, metal sheets or films overcoatedor laminated with a non-conducting or dielectric layer, and plasticfilms such as epoxy resins, polyimide, polysulfone, polyarylether,polycarbonate (PC), polyethylene terephthalate (PET), polyethyleneterenaphthalate (PEN), poly(cyclic olefin) and composites thereof.

The microcups may be formed by any of the methods as described in thisapplication. After the formation of the microcups, a first conductivelayer (92) is formed on the surface (93) of the microcups which includesthe side surface (93 a), the bottom surface (93 b) and the top surface(93 c) of the partition walls (95). In one embodiment, the firstconductive layer may be formed on only the side surface (93 a) and thebottom surface (93 b). In another embodiment, the first conductive layermay be formed on the side surface (93 a), bottom surface (93 b) and thetop surface (93 c) of the partition walls and in this case the firstconductive layer on the top surface (93 c) of the partition walls may belater removed completely or partially. The first conductive layer is ofa discrete pattern when the conductive layer on the top surface of thepartition walls is completely removed. In this case, the discrete firstconductive layers may be connected to the driving components through viaholes.

The first conductive layer may be formed on the surface of the microcupsby electroless plating, sputtering, vacuum deposition, printing, or acombination thereof. Useful conductive layers may include, but are notlimited to, metal conductors such as aluminum, copper, zinc, tin,molybdenum, nickel, chromium, silver, gold, iron, indium, thallium,titanium, tantalum, tungsten, rhodium, palladium, platinum or cobalt,and the like, and metal oxide conductors such as indium tin oxide (ITO)or indium zinc oxide (IZO), as well as alloys or multilayer compositefilms derived from the aforementioned metals and/or metal oxides, orconductive polymers. Further, the conductive layer described herein maycomprise either a single layer thin film or a multilayer thin film. ITOfilms are of particularly interest in many applications because of theirhigh degree of transmission in the visible light region.

The patterning of the first conductive layer may be accomplished by, forexample, a photolithographic process which comprises steps including (i)coating the conductor film with a photoresist, (ii) patterning thephotoresist by imagewise exposing it through a photomask to, forexample, ultraviolet light, (iii) “developing” the patterned image byremoving the photoresist from either the exposed or the unexposed areas,depending on the type of photoresist used, to uncover the conductivelayer in areas from which it is to be removed (i.e., areas where noelectrode lines are to be located), (iv) using a chemical etchingprocess to remove the conductive layer from the areas from which thephotoresist has been removed and (v) stripping the remaining photoresistto uncover the electrode lines.

Alternatively, the photoresist may be printed onto the first conductivelayer followed by etching and stripping to reveal the conductivepattern.

Still alternatively, the conductive layer may be patterned by dryetching using laser or by laminating an adhesive tape on the microcupsurface and peeling off the conductive layer on selective areas of thesurface.

Still alternatively, the first conductive layer may be patterned byprinting a masking layer on the microcup surface followed by depositinga conductive layer by, for example, vapor deposition or sputtering. Morespecifically, the formation of the first conducting film on the microcupsurface may be accomplished by first printing on the surface astrippable printing material. The printed strippable material defines anarea on the surface where the conductive film structure is not to beformed. In other words, the printed strippable material is substantiallynot present in the area on the surface where the conductive filmstructure is to be formed. A thin layer of a conductive material is thendeposited on the patterned surface, followed by stripping the strippablematerial from the surface, whereby the strippable material and anyconductive material formed thereon are removed, leaving behind apatterned conductive film structure.

Alternatively, the formation of a patterned conductive film structure onthe microcup surface may be accomplished by first printing a printablematerial on the surface that defines an area where the conductive filmstructure is to be formed. A conductive thin film is then deposited onthe microcup surface. In this case, the conductive film adheres morestrongly to the printable material than to the surface without theprintable material. After stripping off the conductive film formeddirectly on the surface using a stripping process that does not stripthe conductive film from the printable material, the conductive filmstructure remains formed on the printable material used to define thearea in which the conductive film structure is to be formed. Thesemethods are disclosed in a co-pending application, U.S. Ser. No.10/422,557 filed Apr. 23, 2003 (corresponding to WO03/091788), thecontent of which is incorporated herein by reference in its entirety.

The first conductive layer deposited, particularly that on the topsurface of the partition walls, may be selectively removed or patternedby, for example, (1) photolithographic exposure followed by etching andstripping, (2) laser dry etching or (3) laminating the conductivelayer/microcup/substrate structure with an adhesive tape followed bymechanically peeling off the conductive layer on the top surface ofpartition walls.

After the first conductive layer is formed on the surface of themicrocups, the microcups may then be filled with a display fluid (96)and sealed with a sealing layer (97) as described in sections above.Optionally, an electrode protective layer may be coated onto the firstconductive layer before the filling and sealing of the display fluid.

If needed, the film structure comprising filled and sealed microcup isthen laminated with a second conductive layer (98) optionally with anadhesive layer (99). If the second conductive layer is deposited by, forexample, thin film sputtering or vapor deposition, a secondnon-conducting substrate layer may be laminated onto the secondconductive layer, optionally with an adhesive layer.

The first conductive layer (92) has a thickness in the range of 1 nm to3000 nm, preferably in the range of 20 nm to 500 nm, more preferably inthe range of 50 nm to 150 nm.

There may be a third conductive layer (not shown) between the filmstructure comprising microcups (90) and the first substrate (91),particularly when a discrete conductor pattern is formed on the filmstructure. The first conductive layer may be of a discrete pattern(i.e., not connected) by, for example, removing the conductive layer onthe top surface of the partition walls.

The second and third conductive layers independently may also bepatterned by any of the methods described above.

In one embodiment, the first conductive layer may be disposed onto thesurface of the microcups by thin film deposition (e.g., sputtering orvapor deposition). In another embodiment, the second conductive layermay be formed on the film structure by thin film deposition, printing orlamination. In a further embodiment, the third conductive layer, ifpresent, may be formed on the first substrate by thin film deposition,printing or lamination and the microcups are formed on the thirdconductive layer.

This display fluid (96) referred to in this aspect of the invention maybe any of the liquid composition/display fluid mentioned above. Forexample, the display fluid may be a liquid crystal compositioncomprising liquid crystals and a polymer matrix or a three-dimensionalpolymer network; or a liquid crystal composition comprising liquidcrystals and a chiral material.

III. Transdermal Delivery Device

The film structure (10) of FIG. 1 may be used in a transdermal deliveryfilm. Examples of the liquid composition suitable for transdermaldelivery devices are discussed in Section I.2. The formation of asealing layer which may serve as a diffusion membrane of the deliverysystem is discussed in Section I.3.

FIG. 8 depicts an example of a transdermal delivery system of thepresent invention. The film structure (80) comprises one or moremicrocups which are filled with a liquid composition (81) containing anactive ingredient. Each of the microcups is sealed with a sealinglayer/diffusion membrane (82). There is a skin contact layer (83) whichhas some adhesion property to allow the film structure to be adhered tothe skin of a patient. Any pressure sensitive adhesive layer is suitableas the skin contact layer. The skin contact layer preferably has goodpermeability to water vapor (i.e., perspiration) and air. Suitable skincontact pressure sensitive adhesives may include, but are not limitedto, acrylate copolymers, synthetic rubbers, such as polyisobutylenes,polyisoprenes, styrenes block copolymers, polyvinylethers, siliconepolymers and a combination thereof.

A release liner (84) is placed over the skin contact layer (83). Therelease liner that can be peeled away before use so that thedrug-containing film structure may be exposed. The release layer may beformed from a polymer known in the art which is either peelable bynature or from a polymer which is rendered impermeable to the activeingredient by treating the surface with silicone or a fluorocarboncompound which is readily stripped off. The microcups are formed on asubstrate layer (86). There may also be an optional primer layer (85).

The thickness (excluding the substrate thickness) of the transdermaldelivery film is generally in the range of about 5 μm to about 500 μm,preferably from about 10 μm to about 200 μm.

IV. Preparation of Film Structure Containing One Single LiquidComposition

The process is illustrated by the flow diagram as shown in FIG. 6. Allmicrocups are filled with the same liquid composition. The process canbe a continuous roll-to-roll process comprising the following steps:

-   1. Coat a layer of an embossable composition (60) on a substrate    layer (61). The substrate layer may comprise an electrode layer,    depending on the intended final product.-   2. Emboss the embossable composition at a temperature higher than    the glass transition temperature of the embossable composition by a    pre-patterned male mold (62).-   3. Release the mold from the embossable composition layer preferably    during or after the layer is hardened.-   4. Fill in the thus-formed microcups (63) with a liquid composition    (64).-   5. Seal the filled microcups by one of the sealing methods (e.g., UV    curing 65) discussed in Section I.3.-   6. Laminate other layers (e.g., 66) over the filled and sealed    microcups as needed. An adhesive (67) may be used for the lamination    step. The adhesive may be a pressure sensitive adhesive, a hot melt    adhesive, a heat, moisture or radiation curable adhesive. The    laminate adhesive may be post cured by radiation such as UV (68).    The finished film containing the film structure may then be cut (69)    to desired dimensions after the lamination step.

In Step 6, an electrode layer, instead of being laminated onto the filmstructure, may be directly formed on the film structure by a method suchas coating, printing, vapor deposition, sputtering or a combinationthereof. An active matrix driving structure may also be directly builton the film structure.

The preparation of the microcups described above can be convenientlyreplaced by the other methods disclosed in Section I.1.

V. Preparation of Film Structure containing More than One Type of LiquidCompositions

For the manufacture of a film structure containing more than one type ofliquid compositions, additional steps are needed. These additional stepsinclude (1) laminating the already formed microcups with a positivelyworking dry-film photoresist; (2) selectively opening a pre-determinedamount of the microcups by imagewise exposing the photoresist; (3)filling the opened microcups with a first liquid composition; and (4)sealing the filled microcups by one of the methods discussed in SectionI.3. These additional steps may be repeated to create microcups filledwith liquid compositions of different types.

For display applications, the different liquid compositions maycontribute to different colors or other switching properties. Fortransdermal delivery systems, the different liquid compositions may havedifferent active ingredients or different compositions containing thesame active ingredient. These are only a few examples.

More specifically, a film structure containing different types of liquidcompositons may be prepared according to the steps as shown in FIG. 7.

-   1. Coat a layer of an embossable composition (70) on a substrate    layer (71). The substrate layer may comprise an electrode layer,    depending on the intended final product.-   2. Emboss the embossable composition layer at a temperature higher    than the glass transition temperature of the embossable composition    by a pre-patterned male mold.-   3. Release the mold from the embossable composition layer preferably    during or after the embossable composition is hardened.-   4. Laminate the thus formed microcups (72) with a positive dry-film    photoresist (74) and an adhesive layer (73).-   5. Imagewise expose (FIG. 7 c) the positive photoresist by UV,    visible light, or other radiation means to open microcups in the    exposed area. The purpose of Steps 4 and 5 is to selectively open    the microcups in a predetermined area (FIG. 7 d).-   6. Fill the opened microcups with a first liquid composition (75).-   7. Seal the filled microcups (76) by any one of the sealing methods    discussed in Section I.3.-   8. Steps 5-7 described above may be repeated to generate microcups    filled with different liquid compositions in different areas (FIGS.    7 e, 7 f and 7 g).-   9. Laminate the filled and sealed microcups with other layers (77)    if needed. The lamination may be accomplished optionally with an    adhesive (78), such as a pressure sensitive adhesive, a hot melt    adhesive, a heat, moisture or radiation curable adhesive.-   10. Harden the adhesive, if necessary.

In Step 9, instead of lamination, an electrode layer may be directlydisposed onto the film structure by a method such as coating, printing,vapor deposition, sputtering or a combination thereof. An active matrixdriving structure may also be directly built on the film structure.

The filling of the microcups may also be accomplished by metering indifferent liquid compositions at predetermined locations by inkjetprinting. Alternatively, the different components in the liquidcomposition can be dissolved in a volatile solvent, and inkjet printedfirst. After drying, the common liquid compositions may be blanketcoated, followed by sealing.

The preparation of the microcups described in the process above mayconveniently be replaced by the alternative methods discussed in SectionI.1.

The thickness of the film structure of the present invention can be asthin as a piece of paper. The width of the film structure is the widthof the coating web (typically 3-90 inches). The length of the filmstructure may be anywhere from inches to thousands of feet depending onthe size of the roll.

The film structure may be incorporated into a device. It is understoodthat a device may have one or more layers of the film structure.

One of the key advantages of the present invention is that the filmstructure may be manufactured roll-to-roll on a web continuously orsemi-continuously.

A continuous process is demonstrated in FIG. 6 where the embossing andfilling/sealing are carried out continuously without interruption. Asemi-continuous process is a process in which some of the steps may becarried out continuously; but not the entire process. For example, theremay be an interruption between the formation of the microcups and thefilling/sealing steps or there may be an interruption between thefilling/sealing steps and the lamination step.

The process as shown in FIG. 7 may also be carried out continuously orsemi-continuously. In other words, the multiple steps may be carried outcontinuously without interruption or some of the steps may be carriedout continuously but not the entire process.

Furthermore, in either a continuous process or a semi-continuousprocess, one or more of the steps may be carried out in a stop-n-gofashion. The stop-n-go mode may be carried out at regular or irregularintervals.

The film structure of the present invention enables such format flexibleand efficient roll-to-roll continuous or semi-continuous manufacturing.These processes are easily scalable, can be carried out efficiently, atlow cost.

While the present invention has been described with reference to thespecific embodiments thereof, it should be understood by those skilledin the art that various changes may be made and equivalents may besubstituted without departing from the true spirit and scope of theinvention. In addition, many modifications may be made to adapt aparticular situation, materials, compositions, processes, process stepor steps, to the objective and scope of the present invention. All suchmodifications are intended to be within the scope of the claims appendedhereto.

1. An electrophoretic display comprising: (a) microcups comprisingpartition walls and top-openings; (b) an organic-based electrophoreticfluid filled in the microcups, wherein said fluid comprises chargedpigment particles dispersed in a solvent; and (c) a top-sealing layerformed from a sealing composition to enclose the electrophoretic fluidwithin the microcups, the sealing composition comprising: (i) a watersoluble polymer selected from the group consisting of polyvinyl alcohol;polyethylene glycol and its copolymers with polypropylene glycol;poly(vinylpyrolidone) and its copolymers; polysaccharides; gelatin;melamine-formaldehyde; poly(acrylic acid), its salt forms, and itscopolymers; poly(methacrylic acid), its salt forms, and its copolymers;poly(maleic acid), its salt forms, and its copolymers;poly(2-dimethylaminoethyl methacrylate); poly(2-ethyl-2-oxazoline);poly(2-vinylpyridine); poly(allylamine); polyacrylamide;polyethylenimine; poly(sodium styrene sulfonate); polymethacrylamide;and a cationic polymer functionalized with quaternary ammonium groups;(ii) a water-based suspension, a water-based dispersion, a water-basedemulsion, or a water-based latex, each comprising a polymer selectedfrom the group consisting of polyurethane, polyacrylate, polyvinylacetate, polyvinyl chloride, polystyrene, and the copolymer thereof; and(iii) water; wherein the top-sealing layer is on top of, and in contactwith, the electrophoretic fluid.
 2. The electrophoretic display of claim1, wherein the water soluble polymer is polyvinyl alcohol, polyethyleneglycol, a copolymer of polyethylene and polypropylene glycol,poly(vinylpyrolidone), or a copolymer of poly(vinylpyrrolidone) andvinyl acetate.
 3. The electrophoretic display of claim 1, wherein thewater soluble polymer is poly(acrylic acid), poly(methacrylic acid),poly(maleic acid), poly(2-dimethylaminoethyl methacrylate),poly(2-ethyl-2-oxazoline), poly(2-vinylpyridine), poly(allylamine),polyacrylamide, polyethylenimine, polymethacrylamide, or a cationicpolymer functionalized with quaternary ammonium groups.
 4. Theelectrophoretic display of claim 1, wherein the water soluble polymer isa polysaccharide selected from the group consisting of cellulose,poly(glucosamine), dextran, guar gum, and starch.
 5. The electrophoreticdisplay of claim 1, wherein the water soluble polymer is a cationicpolymer functionalized with one or more quaternary ammonium groupsselected from the group consisting ofpoly(2-methacryloxyethyltrimethylammonium bromide) and poly(allylaminehydrochloride).
 6. The electrophoretic display of claim 1, furthercomprising a water soluble or water dispersable UV curable monomer,oligomer, or polymer.
 7. The electrophoretic display of claim 6, whereinthe water soluble or water dispersable UV curable monomer, oligomer, orpolymer is ethoxylated or propoxylated mono, bi, tri, or multifunctionalacrylate; ethoxylated or propoxylated mono, bi, tri, or multifunctionalmethacrylate; or polymers comprising polyethylene glycol.
 8. Theelectrophoretic display of claim 1, further comprising a water solubleor water dispersable thermal crosslinker.
 9. The electrophoretic displayof claim 8, wherein the water soluble or water dispersable thermalcrosslinker is polyisocyanate, multifunctional polycarbodiimide,multifunctional aziridine, a silane coupling agent,boron/titanium/zirconium based crosslinker, or melamine formaldehydes.10. The electrophoretic display of claim 1, further comprising twoelectrode layers and the filled and sealed microcups are sandwichedbetween the two electrode layers.
 11. The electrophoretic display ofclaim 1, further comprising one electrode layer and one temporarysubstrate layer and the filled and sealed microcups are sandwichedbetween the electrode layer and the temporary substrate layer.
 12. Theelectrophoretic display of claim 1, wherein said temporary substratelayer further comprising a conductive layer or said temporary substratelayer is conductive itself.